Cartesian Graph Paper:

Cartesian Graph Paper is the simplest and most common graph paper in use today. It's most distinguishing feature is that it has a uniform square grid made of intersecting perpendicular lines. You can adjust your graph sheets with two settings for units of measure, choose from eight different primary colors, and a grid size ranging from 1 to 25 lines per inch or a grid with lines separated from 1 to 25 millimeters.

Engineering Graph Paper:

Engineering Graph Paper differs from Cartesian Graph Paper in that it has a multiple width grids. There is a selection of two different grid settings, the primary grid and a second sub increment grid size with the first grid setting being for the wider of the two differing width grid lines. Common settings for this grid setting are usually 5 or 10 time as wide as the sub-increment setting. For example; you might choose 1 per inch for the primary grid and 10 per inch for the sub-increment setting, or you could choose 10 mm or 20mm for the primary grid and 2 mm for the sub-increment grid.
Introduction / Instructions